I'm relying on memory here, which generally I deplore, feeling as I do that you are entitled to a citation if I trot out this sort of reference, but, for what it may be worth, I believe there are places in North America where versicolor is considered a problem or potential threat to other species, genera, or habitats, but is not necessarily considered "invasive" per se, because it is also native to the continent, if not to the area in question. Any vigorous, adaptable, plant, including the beautiful Iris pseudacorus, Shakespeare's "Vagabond Flag," and surely some of the Delta irises, can become a problem plant or ecological disaster in the right--or wrong--circumstances. I take comfort in my firm conviction that SIGNA members are sensitive to these issues.
And there is this, a lagniappe offered in the interest of keeping balance in our discussions, a demonstration, if you will, of how apparently far from reason these concerns can drift.
Denise Adams' book, Restoring American Gardens 1640-1940, from Timber Press, 2004, features an appendix entitled "Potentially Invasive Heirloom Ornamental Plants." Several irises are included in this list, with notes on the jurisdictions in which they are considered causes of concern, and the degree to which that is the case.
In most of the country--I'm talking USA here--pseudacorus is considered a highly problematic non-native plant. In the North Eastern states--and these are Adams' geographical definitions-- and the Pacific Northwest, it is considered a noxious weed by at least one state in that region. Other parts of the country--- with the exception of Illinois and the Upper Midwest generally, including Ohio, and Michigan-- are merely cautious.
Somewhere in Adams' Pacific Northwest region several other Iris species have also been declared "noxious weeds." These weeds include, Ii. cristata; ensata; germanica; pallida; pumila; siberica; xiphium.
Cordially,
AMW
-----Original Message-----
From: Kenneth Walker <kenww@astound.net>
To: iris-species <iris-species@yahoogroups.com>
Sent: Tue, Sep 18, 2012 8:19 pm
Subject: Re: [iris-species] Seed Exchange
I've only ever heard of
I. pseudacorus as being seriously invasive among members of the genus; it is considered to be a problem around waterways in numerous places. The other "problem" iris that I've heard about are:
- Iris foetidissima - in New Zealand, not anywhere else that I know of
- Iris douglasiana - in cow pastures in its native habitat. It's inedible and seems to like sprouting in ground that's been churned up by cattle.
- Iris missouriensis - same as douglasiana
None of these seem to be viewed as invasive plants in general, though you probably couldn't bring them to Hawaii.
While I don't particularly object to keeping "generic"
I. pseudacorus seeds out of the seed exchange, I do agree that seeds of plants with uncommon characteristics (large/small/pale flowers/dark flowers/different markings) or wild-collected seeds from its native range (not US) are good to include.
Ken Walker
On 9/18/2012 2:04 PM, C*@aol.com wrote:
when other water irises, which might arguably be considered equally invasive, are not.
